1. Technical Field
The invention relates to a method for monitoring various physical conditions of a pneumatic tire and to a tire having a memory device containing stored information relating to the tire, and a monitoring device. More particularly, the invention relates to a method and tire construction in which the memory device attaches to the tire innerliner and contains electronics to maintain stored data regarding the tire, preferably an antenna and a low powered battery to transmit and receive data to and from the monitoring device mounted on the tire rim. The monitoring device incorporates a sensing package to interpret temperature and pressure of the tire and has a larger longer life battery than the memory device for communicating with the memory device within the tire and for transmitting and receiving data to and from a source remote. These two separate devices enable the memory device on the tire to be reduced in size and cost and provides a longer service life thereto.
2. Background Information
It is desirable to monitor the condition of tires as to wear, internal temperature and internal pressure. It is particularly advantageous to monitor large truck tires since these are expensive and must be regularly maintained to maximize vehicle efficiency. In the past, such monitoring activities have generally used a passive integrated circuit embedded within the body of the tire and activated by a radio frequency transmission which energizes the circuit by inductive magnetic coupling. Passive devices which rely on inductive magnetic coupling or capacitive coupling generally have the disadvantage of requiring lengthy coil windings, thus requiring major modifications in the tire construction and assembly process. Another serious disadvantage with such passive devices is that the interrogator must be positioned in very close proximity to the tire, usually within a few inches of the tire, in order to allow communication between the tire and the device. Because of the proximity requirements, continuous monitoring is impractical since it would require that an interrogator be mounted at each wheel of the vehicle. Manual acquisition of data from the passive devices embedded in each of the tires of a parked vehicle is also cumbersome and time consuming because of the proximity requirements.
Other prior art devices used for monitoring tire conditions have comprised self-powered circuits which are positioned external of the tire, such as at the valve stem. Externally mounted devices have the disadvantage of being exposed to damage, such as from weather and vandalism. Another disadvantage with installing devices external of the tire is that the device itself introduces additional sealed joints from which air may leak. Additionally, externally installed devices can easily become disassociated from a particular tire which is being monitored.
Another disadvantage with known tire monitoring and identification devices is that communication transmissions are achieved using conventional radio frequencies which generally require a relatively large antenna which must be mounted externally or secured to the tire in such a manner which requires relatively major modifications in the tire construction or assembly process.
Many of these problems have been eliminated by the method and tire construction shown and described in U.S. Pat. Nos. 5,500,065; 5,562,787; 5,573,610 and 5,573,611. However, for certain applications and tire constructions, especially when the tire will be retreaded, it is desirable to protect the sensors from excessive heat which occurs during the retreading process, and for certain applications to provide the tire with only a part of the complete monitoring package by providing a simplified memory device which can be incorporated into the tire either at manufacture or applied after manufacture, and used with or without more detailed sensors depending upon the particular application in which the tire will be utilized.
Although the method and tire monitoring devices shown and described in the above four mentioned patents provide many advantages over the prior art, it is desirable to provide for a tire monitoring system which provides greater versatility by embedding only certain components within the tire at the time of manufacture or separately applying the same to the tire after manufacture, which components are less susceptible to damage by heat and wear, for example, during vulcanization and retreading of the tire, yet which are adapted to be compatible with other components of the monitoring system, which components need not be permanently installed within the tire at time of manufacture, and which most importantly enables a larger and longer life power source to be utilized than is achievable with prior art monitoring systems.